The stars are important to mankind from various perspectives: from them, astrophysicists can deduce not only the laws of celestial mechanics, but also the history and age of the universe.
In observing celestial bodies, it must be kept in mind that the optical telescopes, radiotelescopes or the like used for this purpose cannot remain constantly aimed at a given single point in the sky. Although the stars do remain relatively stationary in the heavens, the earth rotates on its axis once every 24 hours, thus causing every point in the sky to drift continuously across our celestial sphere. The mounting of an optical instrument must therefore be able to track continuously.
The sun is, naturally, particularly important among the celestial bodies, giving us life, light and warmth, and it thus will be used more extensively in the future to supply mankind with energy.
For several decades, technologists and engineers worldwide have devoted themselves to the design of systems by which the energy from the sun's rays can be captured and made technically usable. However, the technical exploitation of solar energy has only recently become efficient enough that it promises to be financially profitable, primarily because suitably efficient components are now available (especially in the field of photovoltaics) for absorbing and converting the energy transmitted by the electromagnetic waves in the form of light rays or solar rays.
Twenty years ago, the technology for harnessing solar radiation for use in converting heat into electrical energy basically consisted of suitably concentrating or focusing the best available reflectors and mirror apparatuses or parabolic arrays on certain points in order to focus and concentrate the energy there—usually at the focal point of such mirror apparatuses—for example by heating containers of media installed at a central location to cause evaporation, based on the principle of power generation by superheating steam followed by generator conversion; primarily over the past twenty years or so, however, the technology for harnessing solar radiation has shifted toward the use of solar panels, which have become increasingly efficient, especially in the form of flat solar collectors, also known as solar or photovoltaic modules (acronym: PV) or solar cells. Higher-performance crystalline PV modules or PV thin-film technology modules are the standard in use today.
An essential factor in the effort to harness solar radiation in an economically viable manner has always been optimal aiming of the support equipment for energy absorbing units (such as reflectors, mirror apparatuses, parabolic arrays, solar panels, solar cells, PV modules, etc.) according to the position of the sun, specifically so that the maximum yield of solar radiation strikes the energy absorbing unit. The solar energy absorbing or reflecting unit is often held in place by a support system, and in more advanced applications also tracks the position of the sun. Tracking systems for solar applications that are currently on the market and in use, which serve to orient devices for absorbing electromagnetic rays, especially solar rays, to a trajectory, are usually implemented as dual-axis, i.e., they permit tracking about two different axes, such that the surface of the modules concerned is always oriented tangentially to the sun and the rays from the sun thus strike the particular module perpendicularly.
For example, DE 294 39 44, published in 1981, describes a device for independently rotating an aggregate about two mutually perpendicular axes, in particular for tracking solar collectors, in which the drive shaft of a first, fixed drive mechanism, basically consisting of a housing, an electric motor, a multi-stage planetary gear set and a spur gear stage, carries at a free end the housing of a second, rotating drive mechanism that basically consists of the housing, an electric motor, a multi-stage planetary gear set and a spur gear stage, and the drive shaft of which, oriented perpendicularly to the drive shaft of the first drive mechanism, carries at its free ends the aggregate that is to be rotated.
Thus, whereas with dual-axis tracking systems the arrangement as a whole can be made to track at any time and even simultaneously in the vertical and horizontal directions (i.e., in elevation and azimuth), single-axis tracking systems allow tracking only in a single direction, i.e., electively either solely in an approximately vertical direction, also referred to as elevation, or only horizontally, also referred to as azimuthally; thus, according to the definitions prevailing in the current state of the art, a single-axis solar collector tracking in a horizontal direction, i.e., about a vertical axis, points due south at 0° azimuth, such that solar rays coming from the south strike the energy absorbing unit in an optimal manner; due east at −90°, due southeast at −45°, due southwest at +45° and due west at 90°, while the inclination to the vertical must remain unchanged in such a case, due to the lack of a second rotational or pivot axis.
At the same time, a single-axis tracking system already offers output advantages of up to 30% over a fixed southward-facing array, whereas with dual-axis tracking up to 45% more output can be achieved with an optimally designed system. Dual-axis tracking systems thus yield better outputs, but are more complex and thus higher in cost and more trouble-prone. In view of these interrelationships, the present invention favors the principle of single-axis tracking.
Such a principle is disclosed by the patent EP 0 114 240, granted in 2004; specifically, a single-axis linear tracking system for a solar collector array comprising at least one torsion tube oriented in a north-south direction and bearing a row of flat, rectangular solar collectors. A horizontal pushrod is able to move a plurality of rows of solar collectors.
Additional prior art that may be cited is the US patent document US 2011/0023940 A1, which describes a single-axis tracking collector system for solar energy. There, the rotational drive used is in fact a slewing unit, in which a rotating part is pivotably disposed inside a housing. Since the housing embraces the rotating part on an end face, it is not possible to fasten a support structure to said end face; this can be done only on one side, on the opposite end face. The resulting design is highly complex and has a relatively low load capacity, such that several extra bearing units are always necessary in addition to a rotational drive unit.
Briefly summarized, the prior art in general has the following disadvantages and characteristics:
1. Building-integrated solutions on carports or on buildings do not track and are usually fixedly integrated in the current state of the art. Non-tracking systems have disadvantages in terms of yield, however.
2. Roof-integrated solutions on buildings, particularly on flat roofs, are always connected to the building in the current state of the art, usually via a force fit, for example screwed or doweled or integrated via snap-together systems. The surface (skin) of the roof is usually manipulated as a result, most often penetrated or damaged in a controlled manner, if only for the deliberate placement of fasteners for the roof-integrated solutions. Since roofs are always exposed to environmental influences, deep installation holes, bores, screw connections, etc., must be sealed after the fact, or least installed in such a way that wind and weather will not damage the structure later on.
3. Dual-axis tracking systems are more expensive than single-axis tracking systems. At this point, dual-axis tracking systems exist only as free-standing systems. Moreover, tracking in elevation with these systems is always accomplished using highly specialized linear actuators.
4. Single-axis tracking systems generally have a limited tracking range, for example with regard to about an axis in an east-west direction.
5. All the commercially available systems to date have consistently been designed for one of the following areas of application: either for free-standing systems or for roof-integrated systems or for building-integrated installation. It is a tremendous disadvantage that no technology associated with the current systems lends itself to a fundamental arrangement that can be used in all the aforesaid fields of application.
From the disadvantages of the described prior art comes the problem initiating the invention: to avoid the disadvantages of the prior art so as to create an inexpensive system for tracking a celestial body that can be used not only as original equipment, but also as a retrofit system on existing floor space or open space or buildings.